Vanadium oxide fluoride-graphite intercalation compounds: Structural characteristics and electrochemical insertion of lithium cations
- Univ. Pierre et Marie Curie, Paris (France). Lab. d`Electrochimie
- Iwate Univ., Ueda, Morioka (Japan)
- Kyoto Univ. (Japan)
Graphite intercalation compounds of vanadium oxide fluoride, C{sub x}(VOF{sub 3})F, were synthesized in a fluorine atmosphere. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction measurements were used for their structural characterization. These experiments have suggested that cointercalation of fluorine and VOF{sub 3} in the carbon occurs involving local structural modifications and that excess oxygen was present in the graphite layers. The study of electrochemical insertion of lithium was carried out at 25 C in a LiClO{sub 4}-propylene carbonate electrolyte by chronopotentiometry and ac impedance measurements. The interfacial charge-transfer process, associated to the half-reaction occurring during the intercalation, was found to be independent of the intercalation ratio of lithium cations, y. The chemical diffusion coefficient, {tilde D}{sub Li}, and the conductivity, {sigma}{sub Li}, obtained were deduced from impedance data by considering the geometric surface area. Both are roughly constant for all the y-range: {tilde D}{sub Li} = 3.8 {times} 10{sup {minus}10} cm{sup 2}/s and {sigma}{sub Li} = 9.3 {times} 10{sup {minus}7} {Omega}{sup {minus}1} cm{sup {minus}1} for C{sub 17.7}(VOF{sub 3})F; {tilde D}{sub Li} = 4.5 {times} 10{sup {minus}10} cm{sup 2}/s and {sigma}{sub Li} = 2.7 {times} 10{sup {minus}7} {Omega}{sup {minus}1} cm{sup {minus}1} for C{sub 20.4}(VOF{sub 3})F.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 367758
- Journal Information:
- Journal of the Electrochemical Society, Vol. 143, Issue 7; Other Information: PBD: Jul 1996
- Country of Publication:
- United States
- Language:
- English
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